Insulator for heaters for electron discharge devices



Aug. 23, T932. H. CROWLEY INSULATOR FOR HEATERS FOR ELECTRON DISCHARGE DEVICES Filed Dec. '7, 1929 [721447260] )hnr L Crow/e kgj/i/s Patented Aug. 23. 1932 nEimY.i..-.cnowm!.br;mroamn nnw masnmnssmnon T0 HENRY L. CROWLEY msunaronm 1 a co. rim, or omen, m A CORBORATION or new JERSEY rzriiccristor visor-mass nmncns 7.132s. serial flo'. 412,333.

This ,invention relates in general uto an insulating ceramic spacer Ember-"to be "used in the heater -element of electron fiiachnr devices betweenthe heater and "thescathotfel One of the objects-of this inventionis the provision of a spacer element :ior such devices which permitszof a decreaseintlle heating time mired to cause full emission of electrons r initial energization of the heater.

Another: object of this-inventionds the provision of a spacer element .ofthistype which gives increased [life to electron, discharge devices in .whic'hu it. is e A still further ObjOOtJdf *thia'mventim :is

to provide a SPRCBI'HIemEHtQOfthQXQbOYG type.

ofysuch form as to improve the quality of output of electron discharge/devices reducmg the noise, :hum and the like normally encountered in useofsuch Y A further object of this intention is the provision of 1 a spacer nf'theabovmtgpe which is of such form as to eliminate themi'crm phonic noise due to the relative movement etween the heater and the spacer.

These and other objects as will appear from the following disclosure are secured by means of this invention.

This invention resides substantially in the combination, construction, arrangement and relative location of parts, all as will be described in greater detail below.

Referring to the drawing Fig. l is a perspective view of a ceramic spacer body made in accordance with the principles of this invention;

Fig. 2 is a side elevationalview of this spacer.

In electron discharge devices such as vacuum tubes employed in radio circuits at the present time, especially those which are energized by alternatin current use a cathode, a heater for the cat ode, and an insulating body between the cathode and heater by means of which they are held in proper spaced relation. Many attempts have been made to form this insulatin body in such a manner that the time required to heat up the cathode where it gives off electrons will be decreased. Likewise, attempts have been made to so construct the insulating body that it will have no deleterious effect on the life of the heater. element, and will not, because of relative movement with respect thereto,v

produce undesired noises when the'deviceis in-use.- One of thereasonsfor the slowness in the heating up of such indirectly heated cathodes, as are'now known, is the mass. of the spacer element and the thickness of-thev walls thereof. The general purpose of this invention is to decrease the time required .for heatingup the device, reduce thethickness, of the walls of the spacer element without impairing its insulating qualities, increase the life of the device and decrease the production of undesired noises, when in use.

The manner in which these advantages are secured will be more readily understood by reference to the drawing. The insulating spacer body 1 is shown, for purposes of illus-- tration, with an approximately oval or ellip= tical cross section having twopassages 2-2 extending longitudinally therethrough from.

end to end. These passages are separated by atransver'se wall 3. As is shown in'the'draw,-

ing,.the thickness of all the walls is the same. By a construction of this type theseflwalls maybema'de relativelythin to effect a reduction-in the mass of the insulator, and a re-; duction in the time required for the heat to travel from the heater to, the cathode which surrounds the heater and fits it snugly. The

heater which is usually in the form of a' straight or coiled wire filament :passes through the passages 2 throughout their length. .The. insulat ng body has been, of

course shown in the drawin considerabl enlarged, inorder to clearly illustrateits con-,

struction, but it is to be understood that it is,

a relatively small thing in actuality. By making the passages of the form shown, it-

is possible to make the walls of the insulator relati-vely'thin, and. of uniform thickness throughout. It is, of course, apparent that any form which accomplishes these purposes fallswithinthe spirit and scope of this invention. Another feature of thesepassages.

is illustratedby pointing out that if the heater fitted snugly in the passages the relative movement between'the heater andthe insulating body produces undesirable sounds when the device is in use. If the passages are a little larger in cross section than the heater similar undesired results are secured, but if the holes are of sufiicient size with respect to the filament considerable improvement is secured. The holes in practice should be sufficiently large to leave the filament practically free, so that if relative movement does occur between the filament and the insulating body the filament will not be in contact therewith.

In practice the general width of the body as indicated by A in Fig. 1 may be 0.062". The width of the transverse wall 3 indicated at B may be 0.042. The width of the passages 2 may be, at the point indicated by C, 0.016". The thickness of the walls as indicated at D may be 0.016". These dimensions are given as examples, and not in a limiting sense. If the round holes of the insulator disclosed in the copending application of Henry L. Crowley, Serial No. 370,789, filed June 14, 1929, are say from 0.065" to 0.016", a reduction in area of 12% is secured while with the construction shown in th s case a reduction in area of 37% is secured. It will be at once apparent, therefore, that by means ofthis construction the mass of the insulator may be materially reduced, without seriously interfering with its use for the intended purpose.

The life of the heater is increased because of the fact that a better heat distribution is efiected in all directions, and the heat is more rapidly transmitted through the walls of the insulator because of their uniform thickness and relative thinness. By reason of having the heater relatively free in the passa es the filament heats up faster and reaches a igher temperature and has a higher resistance so that a larger wire can be used for the same operating current. The life of the heater is increased by reason of the use of a large wire and because the damaging current surge is minimized. The filament being free in the passage is not cooled appreciably by the cold insulator and as a result its resistance rises rapidly preventing or decreasing the initial current surge.

The insulating body of this invention may be made of extruded powdered metal oxides, in accordance with the copending application of Robert M. Crowley and George B. Crowley, Serial No. 344,091, filed March 2, 1929.

I am of course well aware that some changes in the form and construction of the device may be accomplished by those skilled in the art without departing from the principles of this invention, and I do not, therefore, desire to be limited to the disclosure as given for pur ose of illustration, but rather to the scope o the appended claims.

WVhat I seek to secure by United States Letters Patent is:

1. A heater device for radio tubes comprisprisin a tubular member of insulating ing a tubular insulatingmember having a pair of passages extendin longitudinall therethrough forming wal of uniform t 'ckness throughout, and a heater wire passing loosely through said passa es.

2.. A heater device for radio tubes comprising atubular member of insulating material having two passages therethrough separated by a transverse wall, said transverse wall and the walls of said body being of uniform thickness, and a heater'wire passing loosely through said passages. y

3. A heater device for radio tubes commaterial aving a air of semi-elliptica passages extendm t herethrough separated y a transverse wa and a heater filament paming loosely through said passages.

4. A heater device for radio tubes comprising a heater filament, an insulating support and spacer member for said filament compris ing a tubular ceramic body having a air of longitudinal passages, each passage aving a cross section man times greater than the cross section of the lament, and the walls of said tubular member being of substantially the same thickness.

5. A heater device for radio tubes comprising an elliptical shaped tubular insu ator member having a transverse wall extending 05 across the minor axis of the tubular element, the elliptical walls and transverse walls being of substantially the same thickness, and a heater filament loosely passing through said tubular element on opposite sides of said transverse wall.

In testimony whereof I have hereunto set my hand on this 6th day of December A. D.

HENRY L. CROWLEY. 

